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hy·dra

(hīdrə)

n. pl. hy·dras or hy·drae (-drē)

Any of several small solitary freshwater hydrozoans of the genus Hydra and related genera, having a cylindrical body and a mouth surrounded by tentacles.

[New Latin Hydra, genus name, from Latin Hydra, Hydra; see HYDRA.]

Indo-European & Semitic Roots Appendices

Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

Indo-European Roots

Semitic Roots

The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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